While many would argue that that amazing story isn't told too well, I think the main reason people dislike the prequel trilogy is because of the many ways it forces bad retcons on the original trilogy. Granted, the original trilogy had many retcons, but most (not all) worked very well for the story. The fact that Lucas felt compelled to return to the original films again and alter things just to tie it in better with the prequel trilogy speaks volumes about how poorly it was planned.

However, I don't strongly dislike the prequels. I enjoy watching them. I don't think they're up to the caliber of the originals at all, and trying to tie it together with the original leaves a bad taste in my mouth (which is why I rarely ever think of the prequels when I'm watching the originals), but I do enjoy seeing them from time to time. They have some pretty good moments in them. You just have to wait a bit for them. ^_~